The invention relates to an air distribution system for providing rinse air to a gas cleaner, said air distribution system comprising:                a filter housing        a holding plate wherein holes are arranged in concentric circles for holding filter bags or filter elements in the filter housing,        filter bags or filter elements,        rinse air supply, and        an air distribution device for distributing rinse air,        
The invention further relates to an air distribution device for providing rinse air to a gas cleaner provided with filter bags, said air distribution device comprising:                an air distribution member in form of a hollow member,        a connection to an air supply means for rinse air,        
To distribute rinse air in an air cleaner or filter it is known to use an air distribution disc. Such a distributing device is disclosed in U.S. Pat. No. 4,220,457 showing a cyclone comprising a cylindrical housing with tangential entrance for dust-containing air. The lower end of the cylindrical housing of the cyclone is tapered is provided with a dust collector. The opposite upper end of the cylindrical housing is divided by an intermediary wall into a lower dust-containing chamber and an upper dust-free chamber. Filter bags are suspended from the intermediary wall extending into the dust-containing chamber, the filter bags being closed at their lower ends and open at their upper ends.
In use the dust-containing air enters the cyclone via the tangential entrance and large particles are separated off in the cyclone. Smaller dust particles flow upwards with the air in the dust-containing chamber. The dust-containing air enters the filter bags from the outside causing the dust to deposit on the filter bags. The now cleaned air flows further upwards within the filter bags into the dust-free chamber and leaves the air cleaner via an outlet for clean air provided in the dust-free chamber.
After some time of filtering the filter bags may have a rather large amount of dust deposited on their outer surfaces. In order to remove the deposited dust, rinsing air is blown through the filter bags in countercurrent, i.e. from the dust-free chamber to the dust-containing chamber through the filter bags.
U.S. Pat. No. 4,220,457 discloses an arrangement for controlling the blowing of rinsing air in such a way that the filter bags are alternately rinsed during operation. The arrangement comprises a plane, disc-shaped air distribution disc having two diametrically opposite apertures. The air distribution disc is positioned over the upper ends of the filter bags, and the two apertures in the air distribution disc are arranged such that they alternately, by rotation of the air distribution disc, is aligned with the filter bags. Above the air distribution disc, tubes for rinsing air is provided, one tubing for each filter bag. The tubes are connected to a device for compressed air.
In use the air distribution disc is rotated slowly, causing filter bags to be rinsed by compressed air in countercurrent each time the apertures of the air distribution disc are aligned with the rinsing air tubes and the filter bags.
The air distribution disc should be in sealing engagement with the rinsing air tubes in order to prevent any leakage of rinsing air when the tubes are not aligned with the apertures of the air distribution disc. In use, however, practice has shown that the sealing engagement is hard to maintain due to the friction between the air distribution disc and the sealing surface of the tubes. In fact, the friction between the air distribution disc and the sealing surface of the tubes provokes the air distribution disc to expand, especially in the area around the apertures, butt since the air distribution disc is an almost closed disc, the outer area of the air distribution disc tends to bend out of the plane of the air distribution disc, causing a gap to arise between the air distribution disc and the sealing surface of the rinsing air tubes. A large amount of rinsing air may be lost because of this gap. This problem is even worse when hot air is rinsed, due to the high temperatures.
Further it is a problem with filters of large diameters if an air distribution disc as described above is used because either it is necessary to use a disc with a relative large material thickness which will result in a heavy distribution disc or it is necessary to supply an effective sealing to the distributor. These two solutions both require driving means for rotating the disc, which driving means thereby tends to be more heavy and space consuming and more expensive.
A solution to this problem has been to provide a rigid supporting plate underneath the air distribution disc, supporting the air distribution disc by rubber supports between the supporting plate and the air distribution disc, trying to force the air distribution disc not to bend out. This solution has the disadvantage that when the sealing means of the rinsing air tubes are worn, the same problem as described above reappears. Further, the rubber supports are not suitable when rinsing hot air.
Another solution is to reduce the diameter of the apertures, causing lesser expansion of the air distribution disc but requiring higher rinsing air pressure.